High-throughput neuraminidase substrate specificity study of human and avian influenza A viruses.

Despite the importance of neuraminidase (NA) activity in effective infection by influenza A viruses, limited information exists about the differences of substrate preferences of viral neuraminidases from different hosts or from different strains. Using a high-throughput screening format and a library of twenty α2-3- or α2-6-linked para-nitrophenol-tagged sialylgalactosides, substrate specificity of NAs on thirty-seven strains of human and avian influenza A viruses was studied using intact viral particles. Neuraminidases of all viruses tested cleaved both α2-3- and α2-6-linked sialosides but preferred α2-3-linked ones and the activity was dependent on the terminal sialic acid structure. In contrast to NAs of other subtypes of influenza A viruses which did not cleave 2-keto-3-deoxy-d-glycero-d-galacto-nonulosonic acid (Kdn) or 5-deoxy Kdn (5d-Kdn), NAs of all N7 subtype viruses tested had noticeable hydrolytic activities on α2-3-linked sialosides containing Kdn or 5d-Kdn. Additionally, group 1 NAs showed efficient activity in cleaving N-azidoacetylneuraminic acid from α2-3-linked sialoside.